Oral cancer is a devastating disease that impacts 640,000 people worldwide. Though treatment with photodynamic therapy can be effective with significantly less morbidity than alternative therapies, problems arising from less than optimal light delivery to the oral cavity have hindered its widespread application. The goal of the proposed research is to provide a new class of single-use sources that are effective, affordable and convenient. These devices will overcome current device limitations to deliver a uniform irradiance to the treatment region and margin, resulting in more predictable and reproducible clinical outcome. Also, by providing inherent shielding of normal tissues of the oral cavity, they will greatly reduce the time and effort needed to prepare a patient for a PDT session. An initial set of 12 devices will be constructed for an anticipated clinical evaluation in Phase II of the proposed investigation. These will be tailored to treat common oral cancer sites including the lateral border of the tongue, ventral tongue, gumlineand floor of the mouth. The source design will leverage proof-of-concept engineering established in the preliminary studies, and each resulting device will be characterized radiometrically. Device performance will be modeled in a graphical-processor-unit based Monte Carlo simulation that will explicitly incorporate the radiometric data and characterize a previously unreported source-tissue feedback mechanism. At the conclusion of this one-year investigation, we will be in a position to subject these devices to clinical evaluation in collaboration with Roswell Park Cancer Institute.